1. Field of Invention
This invention relates generally to paper-plastic laminate sheeting capable of being converted into envelopes, bags and other dilatable container products which initially are in a flat state and are normally made of paper, and more particularly to a laminate sheeting in which a paper facing sheet is cold-laminated to an oriented film of synthetic plastic material.
2. Status of Prior Art
The sheeting traditionally used in making envelopes, grocery bags and other types of dilatable container products which initially are in a flat state is paper. Paper is a semi-synthetic material made by chemically processing cellulose fibers.
Apart from its low cost, an important advantage of paper is that it can be converted into envelopes and other types of dilatable container products by means of high speed equipment that functions to cut and fold the sheeting into the desired configuration, the folds and flaps of the product being bonded together, where necessary, by standard low-cost adhesives. Another advantages of paper in this context is that it can readily be printed and colored, using standard inks for this purpose.
But such paper products suffer from several disadvantages, for they are characterized by low tear and burst strength, and are by no means water resistant; for unless coated, paper is highly absorbent.
Also well known in the art are plastic-coated cellulosic papers, these being used chiefly in children's books, posters, signs and shipping tags, and for other purposes demanding resistance to hard wear and to outdoor exposure. However, such plastic-coated papers lack high tear and burst strength. Also low in strength are special purpose coated papers covered on one or both sides with a suspension of clays, starches, rosin or wax, or a combination of these substances.
To overcome the drawbacks of paper-fabricated dilatable container products, in recent years such products have been made of TYVEC or other polymeric synthetic plastic sheeting. The resultant products not only have a tear and bursting strength far superior to paper, but they are also waterproof.
However, TYVEC and similar synthetic plastic sheeting is difficult to convert into envelopes and other dilatable container products using high-speed equipment of the type mainly suitable for paper. As a consequence, production scrap rates can run as high as thirty percent, thereby raising the cost of manufacturing these products. Moreover, such plastic sheeting has a low chemical affinity for standard adhesives; hence in the case of envelopes, one must then use a special and more costly adhesive on the flaps. And such plastic sheeting also has a low affinity for standard printing inks, and the products, therefore, demand special printing inks for this purpose.